Ah, I see. I was confused because the code doesn't use these vars
anywhere else.

> > Shouldn't those do something more than setting IUSE? For example,
> > actually ensuring those LINGUAS will be installed?
>
> That would be a nice improvement.
>
> We at qt@ have been discussing this on and off. We would like to
> see a linguas.eclass happen, because already now we start having
> code duplication. So instead of this duplication of code between
> qt4-r2 and cmake-utils eclasses, why not put this into a separate
> linguas.eclass that both can inherit?

Yes, it's a much better idea than keeping two copies in sync.

> Obviously the problem with handling more than just setting IUSE
> is the variety of ways in which linguas are handled by different
> packages and different build systems.

Yes, that's one problem. Certainly, those flags have to be handled
by the build system and the disabled LINGUAS should not be built
at all. If there are built already, there's no point in removing them
later.
Of course, another question is whether LINGUAS does actually benefit
users. If compiling another .po files takes a lot of time, probably
yes. If it doesn't, I would think about getting rid of that and just
installing everything. Additional removal can be handled through
INSTALL_MASK.
--
Best regards,
Michał Górny